Power Chords and Guitar-Specific Harmony

The idea

Rock and metal guitar harmony follows its own rules because of distortion.

• The power chord (written E5, A5) is a root and a 5th, usually with the octave on top. It has no 3rd, so it does not clash under gain and it is neither major nor minor. The melody, the bass or the notes around it imply the quality. This ambiguity is a feature: a riff on E5 can feel Aeolian, Phrygian or Mixolydian depending on the single notes around it.
• The inverted power chord puts the 5th in the bass, which makes a perfect 4th: B below E instead of E below B. It sounds thicker and sludgier.
• Drop tunings such as Drop D (D A D G B E) turn power chords into one-finger barres on the three lowest strings. Riffing gets faster and the pitch gets lower. The theory does not change. The geography does.
• Adding color under gain. The safe additions to a power chord are the 9th, the 4th, and a 3rd played high and brief. Full barre chords under high gain turn to mud, which is why metal rhythm guitar lives on two-string and three-string fragments.

On your instrument

The shapes you need, shown from an A root at the 5th fret:

     A5     A5        inverted   A5 plus 9     Drop D
            3 notes   (E under A) stacked 5ths  D5   G5
G|------------------------------------------|-----------|
D|------------7----------7---------9--------|--0----5---|
A|-----7------7----------7---------7--------|--0----5---|
E|-----5------5--------------------5--------|--0----5---|

• The stacked-5ths shape (A, E, B: root, 5th, 9th) is the wide, clean-under-gain chord of The Police and of a lot of modern rock.
• Playing technique matters as much as the notes. Palm muting shortens and darkens the chord. Open, unmuted chords sound bigger. The contrast between the two is the basic dynamic tool of rhythm guitar.
• Mute what you do not play. Under gain, every open string that rings by accident is part of your chord.

Piano equivalent. Play the root and 5th in the left hand, low, and put any color notes two octaves higher in the right hand. This is the same principle as on a distorted guitar: keep the bottom simple and spread the color out on top.

Worked example

One idea, three textures. The progression is E – G – A – E, one bar each.

Texture	How to play it	Result with distortion
Power chords	E5, G5, A5, E5 on the two lowest strings	Clear, heavy, neutral
Full barre chords	E, G, A, E major, all six strings	Thick and blurred. The 3rds grind.
Single notes	E, G, A, E on string 6, palm-muted 8th notes	Tight and aggressive, with room for everything else

All three are valid. The power-chord version is a chorus, the single-note version is a verse, and the full-chord version works when you roll the gain back for a clean or crunchy section. Choosing the texture is half of arranging for guitar.

Exercises

1. Write one 4-bar riff and play it three ways: power chords, full barre chords, and a single-note line on the low string. Under distortion, judge the clarity of each.
2. Take a Phrygian riff from Module 2 and add a power chord on each accented note. This is the classic thrash texture.
3. Play A5, then add the 9th (4:9, with your little finger). Play the same shape from G, C and D. Write a four-chord progression using only these stacked-5th shapes.
4. If you have never tried Drop D: lower string 6 to D, play one-finger power chords on the three lowest strings, and write an 8-bar riff.

Common mistakes

• Turning the gain up to sound heavier. Heaviness comes from tight playing, low register and space. Too much gain hides all three.
• Forgetting that the band decides major or minor. If the bass plays G under your E5, the listener hears E minor. Coordinate.